sump / fuge / overflow

I don't understand how you can prevent a sump from overflowing and dumping water all over the floor. I must be misunderstanding how this works!

From what I understand the sump is filled by gravity, either a siphon-type setup or gravity through a drilled tank. The water then flows through the sump and its pumped out the other end back into the tank. So if the pump dies or loses power, how does it not just fill up the whole sump and flood your floor?

What if your pump cant handle the amount of water being fed int o the sump? It seems to me that is a delicate balance that would need constant attention.

I'm certainly missing something here

 

The way to prevent this is by drilling a small hole in the return line just below the waterline of your main tank. If the pump (or power) fails, the hole will break the siphon as soon as the water falls below it. You just have to make sure that your sump has enough room to hold that water.

Actually, you want the pump to handle less flow that the overflow. If the pump had more capacity than the overflow, it would empty the sump into the main tank and overflow it. With the pump slower that the overflow, a balance is formed in that only as much flow as the pump can put into the main tank will be drained by the overflow into the sump.

 

The sump have to be big enough for "backwash" when the pump fails. The overflow in your tank is supposely half inch to an inch more or less (depending your pump's flow rate) below the water surface, so when the pump failed, water should stop flowing to the sump at that point and you should have a big enough sump to hold that much amount of water before overflowing on your floor. HTH.


Ok, Michael explained it much better than me...

 

Not sure where the appropriate place for this is.

I drew a little picture I wonder if we could use that as a reference because I'm still lost (sigh).

So i would have to start a siphon with the blue hose on the right. This would cause the sump to start filling, but I would take care not to put the blue line too low in the tank so it cant draw enough water to flood the sump. But if the sump pump should not be able move more gph than the filling line, this inevitably draw more water from the tank that was being put back in it. That would leave the right blue line air locked I believe and I'm dead in the water

That's how I'm imagining this all to work but obviously is incorrect 8)

 

As you have your diagram, you are correct, the overflow would break the siphon and that would be that. What you need to use is either a tank with a builtin overflow or an over the top overflow such as Covey's diy overflow.


With the overflow, the siphon is not broken, but the water balances in the two vertical tubes that hang over the tank.

Mike

 

Ok let me see if I can explain this clearly. If you are using an overflow box, the kind the hangs on the tank with the "teeth," then the water has to always be a smidge above the teeth to keep overflowing. The water stays that way because the return pump is constantly pumping water from the sump back into the tank. If the power stops, then so does the return water, and in just a minute, the water will stop overflowing into the overflow box because the return pump isn't pumping water back into the tank to keep the water level above the teeth. Then the whole thing would stop. I hope that makes sense. If not...I tried.

 

Yeah I totally get it now THANKS !

So it seems that my problem was not including a proper overflow design in my lil picture above it seems

Michaelr5, thanks for they DIY pic. I'm assuming that the tube closer to the camera is the one that goes inside the tank? Also, what is the little thing sticking out of the top of the U shaped joint?

Thanks again all I think I finally understand all of this.

 

Yes the tubes closest to the front go in the tank. The thing sticking up is just a check valve to allow the initial priming of the overflow by sucking the air out.

Here is a link to the original thread about the nice-cheap-diy-overflow.

Mike

 

very clever!